Variational bound for the energy of two-dimensional quantum antiferromagnet

TL;DR

This paper derives a variational upper bound for the ground-state energy of the 2D quantum antiferromagnetic Heisenberg model on a square lattice, applicable across different anisotropy levels, using a generalized Jordan-Wigner transformation.

Contribution

It introduces a novel variational method to estimate the ground-state energy of the 2D antiferromagnetic Heisenberg model for arbitrary anisotropy.

Findings

Provides an upper bound for the perturbation series about the Ising limit.

Extends the Jordan-Wigner transformation to two dimensions.

Offers a new analytical tool for studying 2D quantum antiferromagnets.

Abstract

We obtain the variational upper bound for the ground- state energy of two-dimensional antiferromagnetic Heisenberg model on a square lattice at arbitrary value of the anisotropy parameter using the two-dimensional generalization of Jordan-Wigner transformation. Our result can be considered as an upper bound for the perturbation theory series about the Ising limit.